JP7112495B2 - An improved method for estimating arterial blood values - Google Patents

Description

The present invention provides a computer-implemented method for converting a venous blood value to an arterial blood value, a computer-implemented method for measuring a blood value and converting a venous blood value to an arterial blood value. and a corresponding computer program product for carrying out the method in a computer system.

Arterial blood gas analysis is a routinely used laboratory test and point-of-care primarily to assess acid-base status in conjunction with adequacy of ventilation and oxygenation in critically/acutely ill patients. It is a care test.

Assessment of a patient for acute illness is a complex process involving evaluation of many of the patient's physiological systems, including the pulmonary, metabolic, renal, and circulatory systems. Most of the information required for this assessment comes from analysis of the patient's blood. Blood samples can be taken from both arteries and veins. Arterial blood can be sampled either by placing an arterial catheter or cannula in the patient or by performing an arterial puncture with a needle. Venous blood can be sampled from a peripheral cannula or venipuncture (peripheral venous blood), a catheter placed in the superior vena cava (central venous blood), or a pulmonary artery catheter placed in the pulmonary artery (mixed venous blood). .

In patients admitted to the intensive care unit (ICU), the use of indwelling catheters is common to facilitate access to arterial blood. In other clinical departments, arterial blood is usually collected via arterial puncture. Arterial puncture has been shown to be more painful and uncomfortable than venous sampling and carries a risk of side effects to the patient. For clinical staff, arterial puncture is more complicated and carries risks, as the collection system used presents a potential risk of contamination by blood leakage in addition to needle stick injury.

Many of the measurements obtained from blood and used to assess a patient's condition are similar for venous and arterial blood samples. These include electrolytes such as sodium (Na), potassium (K), and hemoglobin concentration (Hb), and concentrations of abnormal forms of hemoglobin (e.g., carboxyhemoglobin (COHb), methemoglobin (MetHb)). rice field.

However, the acid-base status of arterial and venous blood is not the same regardless of the sampling site. Acid-base status generally refers to the following measurements in blood: pH, tension of oxygen (pO2), tension of carbon dioxide (pCO2), concentration of bicarbonate (HCO3), concentration of base above baseline conditions (overbased (BE)), bicarbonate concentration at baseline pCO2 (standard bicarbonate SBC), oxygen tension (pO2), and hemoglobin oxygen saturation (SO2), pO2 and SO2 are referred to as the oxygenation status of the blood. There are many. The difference in acid-base status between arterial and venous blood is due to metabolic deoxygenation and carbon dioxide addition from the blood in tissues.

For this reason, in order to reduce the need for arterial puncture, e.g. for converting venous blood values to arterial blood values, WO 2004/010861 (to OBI Medical Aps, Denmark) is disclosed. A number of new efforts have been made over the years, such as how to他の関連する参考文献は、ＲＥＥＳ Ｓ Ｅ：「Ｔｈｅ Ｉｎｔｅｌｌｉｇｅｎｔ Ｖｅｎｔｉｌａｔｏｒ（ＩＮＶＥＮＴ）ｐｒｏｊｅｃｔ：Ｔｈｅ ｒｏｌｅ ｏｆ ｍａｔｈｅｍａｔｉｃａｌ ｍｏｄｅｌｓ ｉｎ ｔｒａｎｓｌａｔｉｎｇ ｐｈｙｓｉｏｌｏｇｉｃａｌ ｋｎｏｗｌｅｄｇｅ ｉｎｔｏ ｃｌｉｎｉｃａｌ ｐｒａｃｔｉｃｅ」、ＣＯＭＰＵＴＥＲ ＭＥＴＨＯＤＳ ＡＮＤ ＰＲＯＧＲＡＭＳ ＩＮ ＢＩＯＭＥＤＩＣＩＮＥ、第１０４巻、２０１１年１２月(2011-12), pp. S1-S29, TOFTEGAARD M: "A mathematical model based method for converting venous values of acid-base and oxygenation status to arterial values", Ph.D. 01), pp. 1-49, and US Patent Application Publication No. 2007/218559 Al (FRANCO WAYNE P [US]) September 20, 2007 (2007-09-20).

The method of WO2004/010861 has the advantage of not having to take an arterial blood sample, thus eliminating the drawbacks of taking an arterial blood sample compared to a venous blood sample when taking an arterial blood sample. The method basically consists of three steps: first measuring arterial oxygenation, for example by pulse oximetry, preferably by anaerobic sampling, and measuring peripheral venous blood (PVBG) or central venous blood A second step of estimating the venous acid-base and oxygenation status values of a venous blood sample containing (CVBG), the blood acid-base and oxygenation status is converted to the desired arterial blood estimate, i.e. It is based on a third step of transforming the venous blood values by applying a mathematical model to lead to one or more values of acid-base status. The method, which is generally described in WO2004/010861, is currently commercially available from OBI Aps under the trade name v-TAC™ and additional information can be found on their web page www. obimedical. See www.com.

However, improved methods of converting venous blood values to arterial blood values would be advantageous, and in particular, more efficient and/or reliable methods would be advantageous.

A further object of the present invention is to provide an alternative to the prior art.
During the clinical use of the method of WO 2004/010861 on some patients, in some patients and/or in some situations, the method does not give desirable results when arterializing blood gas levels. was discovered.

Estimate arterial oxygenation by pre-analytical and/or analytical error during blood gas analysis, among other factors, and/or using, for example, pulse oximetry, where the accuracy of measurements is usually limited In some cases, it has been discovered by the inventors that a situation may arise in which the corresponding venous oxygenation values are actually higher than the measured arterial oxygenation.

The same situation occurs when using VTAC methods, including v-TAC™, to fully arterialize capillary blood gas samples that may have been mechanically inadequately arterialized prior to sampling. occurring even more frequently. Mechanically arterialized capillary samples will, by definition, be closer to arterial values. This is clearly demonstrated by clinical case (2) in Table 1, where v-TAC failed to arterialize capillary blood in 13 out of 40 data sets (32.5%).

Thus, in approximately 5% of patients undergoing pulmonary therapy when venous blood gases are used, and 20-50% of patients when capillary blood gases are used, clinicians will require arterial This issue is significant in that you will receive an error message instead of the value of As a result, the clinician would have to redo the measurements, such as performing an arterial puncture or capillary sampling. It should be emphasized that this critical problem has heretofore not been recognized in the art, and thus the present invention will establish a solution to a previously unknown problem.

In particular, in a computer-implemented method for converting venous blood values to arterial blood values, using arterial oxygenation measurements that are too low for further use, the above-described prior art It may therefore be considered an object of the present invention to provide a computer-implemented method that solves a previously unknown problem.

To this end, the above object and several other objects, in a first aspect of the present invention, is a computer-implemented method for converting venous blood values to arterial blood values, comprising:
a) providing measurements and/or estimates of arterial oxygenation;
b) measuring and/or estimating blood acid-base status values in a blood sample obtained from venous blood;
c) transforming the venous blood values by applying a mathematical model to derive the acid-base and oxygenation status of the blood to estimates of the arterial blood;
d1) if the measured and/or estimated arterial oxygenation is below the corresponding venous oxygenation value,
e) next, estimating said arterial oxygenation value using a substitute value which is a function of the corresponding venous oxygenation value.

The present invention is particularly, but not exclusively, useful for obtaining arterialized blood gas and acid-base values for a higher proportion of clinical samples and for cases where venous or capillary blood is already close to arterial blood. Computer implemented to convert venous blood values to arterial blood values so that almost all situations can be solved (depending on the setting) and answers can be reliably obtained in clinical use It would be advantageous to provide a method.

In the context of the present invention, the term "converting" is used broadly, i.e., using - but not limited to - a computer-implemented data processing system, for example, to convert one number into another number. It is to be understood to be understood to include determining or calculating.

In the context of the present invention, arterial and venous blood are closely interconnected and arterial blood is oxygenated in the lungs and transported to the capillaries where arterial blood oxygen is used for metabolism and subsequently returned to the lungs. is understood by those familiar with physiology. Depending on the context, there may therefore be a gradual transition from arterial blood to capillary blood and from capillary blood to venous blood.

In the context of the present invention, the mathematical model for deriving or converting blood acid-base status and oxygenation values to arterial blood estimates is based on the following conditions (C1, C2, and/or C3) or May be based on one or more of the model assumptions:
- The C1 respiratory quotient (RQ = VCO ₂ /VO ₂ RQ) is preferably determined by the equation:
RQ= Fe'CO2 _- FiCO2 or RQ ₌ FeCO2 _{- FiCO2} ,
FiO ₂ —Fe′O ₂ FiO ₂ —FeO ₂
is used to measure inspired oxygen (FiO ₂ ) and inspired carbon dioxide (FiCO ₂ ) concentrations and end-tidal oxygen (Fe'O ₂ ) and end-tidal carbon dioxide (Fe'CO ₂ ) concentrations or exhaled oxygen (FeO ₂ ) and carbon dioxide (FeCO ₂ ) combined, and may be estimated by measurements of inspired and expired gases taken in through the mouth.
-C2 RQ approximation according to assumption C1 above can often lead to values that can vary significantly. However, the true values of RQ in tissues are 0.7 for aerobic metabolism of lipids and 1.0 for aerobic metabolism of carbohydrates, and can only vary between 0.7 and 1.0.
and/or - C3 A mathematical model of the acid-base and oxygenation status of the blood is a constant respiratory quotient (RQ ) adding O ₂ and removing CO ₂ from venous blood at a rate determined by ). This simulation may then be performed until the simulated oxygen saturation equals the oxygen saturation estimated or measured in condition C2, ie, the oxygen saturation in arterial blood.

In particular, conditions C2 and C3 have been found by the inventors to yield advantageous results.
For further details regarding specific models see WO2004/010861 (OBI Medical Aps, Denmark), which is also incorporated herein by reference in its entirety.ているＣｏｍｐｕｔｅｒ ｍｅｔｈｏｄｓ ａｎｄ ｐｒｏｇｒａｍｓ ｉｎ ｂｉｏｍｅｄｉｃｉｎｅ ８１（２００６）の１８～２５ページにある、Ｒｅｅｓらによる関連する科学論文「Ａ ｍｅｔｈｏｄ ｆｏｒ ｃａｌｃｕｌａｔｉｏｎ ｏｆ ａｒｔｅｒｉａｌ ａｃｉｄ－ｂａｓｅ ａｎｄ ｂｌｏｏｄ ｇａｓ ｓｔａｔｕｓ ｆｒｏｍ ｍｅａｓｕｒｅｍｅｎｔｓ ｉｎ ｔｈｅ ｐｅｒｉｐｈｅｒａｌ ｖｅｎｏｕｓ ｂｌｏｏｄ」もReference is made, but more details of particular models, other models or variations thereof may be applied within the context and principles of the present invention, as would be readily understood by one skilled in the art.

In the context of the present invention, providing, measuring and/or estimating a blood value from a blood sample does not necessarily involve the specific steps of taking or withdrawing a blood sample from a patient; It is understood that the measurement results may be obtained, forwarded, communicated, etc. from other entities or individuals, e.g., nurses, who performed the blood measurements or draws. It is.

In the context of the present invention, upon receiving the results of the present invention, i.e., by converting the venous blood value to an arterial blood value, the resulting arterial blood value is subsequently used by a clinician or medically trained It is understood that it may be used in the judgment process by those who It is anticipated that the decision process may be automated, for example, as part of a computer-implemented Decision Support System (DSS). For this reason, if arterial blood values in a particular patient under a particular circumstance are outside of physiologically acceptable or normal levels, the following clinical interventions or treatments may be initiated or recommended: be. For example, when arterial blood values for oxygenation are too low, for example, hypoxemia can be a sign of respiratory and/or circulation related diseases or conditions such as anemia, COPD, asthma, or heart disease. .

In one embodiment, arterial oxygenation measurements may be provided by pulse oximetry (Sp02) or other means for non-invasively or invasively measuring arterial oxygenation.

In one embodiment, if condition d1) is met, then the method initiates an additional condition d2) an additional prerequisite for e) that has been found to be useful in the clinical test to be performed As further, the numerical difference between said measured and/or estimated arterial oxygenation value and said corresponding venous oxygenation value exceeds a predetermined threshold (K), e.g., 1, 2, 3, less than 4, 5, 6, 7, 8, 9, or 10 percent. Furthermore, in condition d2), said predetermined threshold (K) is the measurement uncertainty of the measurement device used to provide the arterial oxygenation value in a), e.g. pulse oximetry, and/or It may depend on the measurement uncertainty of the measuring device used in b) to provide the value of the acid-base status of the blood in the venous blood sample, for example a blood gas analyzer.

Beneficially, in the process of e) of estimating said arterial oxygenation value using a surrogate value which is a function of the corresponding venous oxygenation value, said function is derived from arterial blood gas and acid-base status , adjusted to predict arterial oxygenation values.

Advantageously, in the step e) of estimating said arterial oxygenation value using a substitute value which is a function of the corresponding venous oxygenation value, said substitute value is, as an embodiment, said venous oxygenation value May be equal to oxygenation value.

In some embodiments, in the step of e) of estimating the arterial oxygenation value using a surrogate value that is a function of the corresponding venous oxygenation value, the surrogate value is, for example, a blood gas one or more pre-analytical and/or analytical errors in the measurement and/or estimation of venous blood gases and acid-base status by a measuring means or device of and/or arterial as measured, for example, by pulse oximetry It may be adapted to supplement oxygenation and/or presumed arterial oxygenation.

In another embodiment, in step e) of estimating the arterial oxygenation values using a surrogate value that is a function of the corresponding venous oxygenation value, the surrogate value is a metabolic Adapted to complement the predicted minimal oxygen metabolism, which results in corresponding differences between arterial blood gases and acid-base status (ABG) and venous blood gases and acid-base status (VBG), if any. may be

In an advantageous embodiment, in the step e) of estimating said arterial oxygenation values using a substitute value which is a function of the corresponding venous oxygenation values, said function is based on a physiological model, in particular It may include models of arterial blood gases and acid-base status, such as models forming part of and/or in conjunction with VTAC, and measuring venous blood gases and acid-base status ( VBG _M ) and/or estimated venous blood gas and acid-base status are used to predict arterial oxygenation values. In addition, said measured venous blood gases and acid-base status (VBG _M ) are further corrected to compensate for one or more analytical errors in the measurement of venous blood gases and acid-base status (VBG _M ). may be Additionally or alternatively, said measured venous blood gases and acid-base status (VBG _M ) may be combined with arterial blood gases and acid-base status (ABG) and venous blood gases and acid-base status for better results. (VBG) may be further corrected to complement the predicted minimal oxygen metabolism, resulting in corresponding differences between (VBG).

In an advantageous embodiment, the step of c) converting the venous blood values by applying a mathematical model to derive the acid-base and oxygenation status of the blood to an estimate of the arterial blood ( _ABGP ) is , with respect to venous blood measurements ( _VBGM ) may be modified in that oxygen is removed and/or carbon dioxide is added for modeling purposes to obtain better results . Oxygen may be removed and/or carbon dioxide added, particularly for modeling purposes limited to a range of physiologically possible values. Additionally, the arterial blood estimate may be calculated within the range of physiologically possible values.

In some embodiments, in condition d2), the predetermined threshold (K) is a physiologically-based safety margin as would be appreciated by one of ordinary skill in the art once the general teachings of the present invention are appreciated. It can be up to you.

In some embodiments, the mathematical model determines that the true value of respiratory quotient (RQ) in tissue is 0.7 for aerobic metabolism of lipids, 1.0 for aerobic metabolism of carbohydrates, and 0.7 Sometimes it applies that it can only vary between ~1.0. Additionally or alternatively, in another embodiment, the mathematical model includes oxygen O2 is added and carbon dioxide CO2 is removed from the venous blood so that the simulated oxygen saturation equals or substantially equals the estimated or measured oxygen saturation in arterial blood. Until then, it may apply to conduct simulations.

Thus, generally, the subscript "A" means artery, the subscript "V" means vein, the subscript "M" means measured, and the subscript "E" means means presumed, the subscript "P" means presumed, and so on. In some of the figures and/or descriptions, subscripts such as "SO2V" may not be listed as subscripts for practical reasons, but what their technical meaning is is will be understood by those skilled in the art.

In a second aspect, the present invention is a data processing system, preferably computer implemented, for converting venous blood values to arterial blood values, comprising:
- means for providing measurements and/or estimates of arterial oxygenation,
- means for measuring and/or means for estimating values of the acid-base status of blood in a blood sample obtained from venous blood; Transform the venous blood values by applying a mathematical model to lead to
wherein if the measured and/or estimated arterial oxygenation value is below the corresponding venous oxygenation value, then with a substitute value that is a function of the corresponding venous oxygenation value, A data processing system comprising means for estimating said arterial oxygenation value.

In a third aspect, the invention provides a computer system comprising at least one computer, having data storage means associated therewith, to control a system according to the second aspect of the invention. relating to a computer program product adapted to

This aspect of the invention specifically, but not exclusively, performs the operations of the system of the second aspect of the invention when a computer system is downloaded to or uploaded to that computer system. Advantageously, the invention may be accomplished by a computer program product that allows to do. Such computer program products may be provided on any kind of computer readable medium or over a network.

Each individual aspect of the present invention may be combined with any of the other aspects. These and other aspects of the invention will be apparent from the following description with reference to the illustrated embodiments.

The method according to the invention will be described in more detail below with respect to the accompanying figures. These diagrams show one way of carrying out the invention and should not be considered limited to other possible embodiments that fall within the scope of the appended claim set.

FIG. 1 shows a schematic overview of blood flow in a subject; FIG. 2 shows graphs of oxygen dissociation curves (ODC) in three situations; FIG. 2 shows graphs of oxygen dissociation curves (ODC) in three situations; FIG. 2 shows graphs of oxygen dissociation curves (ODC) in three situations; FIG. 2 shows a schematic system chart representing an overview/details of the operation of the computer-implemented method according to the present invention;

FIG. 1 is a schematic overview of blood flow in a subject or patient, using the vTAC™ method, as disclosed in WO 2004/010861 (OBI Medical Aps, Denmark). 1 schematically illustrates a computer-implemented method for performing a prediction of arterial blood acid-base status values from a venous blood sample sampled at .

Arterial blood gas values are estimated or predicted, by way of example, as shown in the following four steps.
Step 1: Anaerobic venous blood samples are drawn and analyzed using standard blood gas analysis techniques to obtain an overview of the acid-base status of venous blood ( _SBCv , _pHv , _pCO2v , _BEv , pO _2v , and SO _2v ).

Step 2: Estimate or measure arterial oxygen saturation non-invasively, possibly by pulse oximetry.
Step 3: CO2 added (i.e. percentage of CO2 production (VCO2)) and O2 removed (i.e. O2 utilization (VO2)) by aerobic metabolism in blood samples passing through tissues from arteries to veins ) is defined as the respiratory quotient (RQ=VCO ₂ /VO ₂ ). RQ is the equation:
RQ ₌ Fe'CO2 _- FiCO2 or RQ = FeCO2 _{- FiCO2}
FiO ₂ —Fe′O ₂ FiO ₂ —FeO ₂
is used to measure inspired oxygen (FiO ₂ ) and inspired carbon dioxide (FiCO ₂ ) concentrations and end-tidal oxygen (Fe'O ₂ ) and end-tidal carbon dioxide (Fe'CO ₂ ) concentrations or exhaled oxygen (FeO ₂ ) and carbon dioxide (FeCO ₂ ) combined concentrations, and are often approximated by measurements of inspired and expired gases taken through the mouth.

Estimation of RQ by this method often results in values that can vary widely. However, the true values of RQ in tissues are 0.7 for aerobic metabolism of lipids and 1.0 for aerobic metabolism of carbohydrates, and can only vary between 0.7 and 1.0. In this step, a mathematical model of the acid-base and oxygenation status of the blood is generated with a ratio determined by a constant respiratory quotient set within the physiologically possible range of 0.7-1.0. ₂ and remove CO ₂ from venous blood. This simulation is performed until the simulated oxygen saturation is equal to the oxygen saturation estimated or measured in step 2, ie the oxygen saturation in arterial blood.

Step 4: Next, the model of blood acid-base and oxygenation status is used to calculate the global picture of arterial blood acid-base and oxygenation status ( _SBCap , _pHap , _pCO2ap , _BEap , pO _2ap , and SO _2ap ). This is supported by simulated removal of CO2 and O2 from venous blood at a fixed RQ, if the simulated arterial oxygenation agrees with the measured arterial oxygenation. is also possible, because the simulated values of the variables of should reliably match the measured values.

For the purpose of testing the venous to arterial conversion method, the predictive values of arterial acid-base status ( _SBCap , _pHap , _pCO2ap , _BEap , _pO2ap , and _SO2ap ) obtained from this method were Their measured values (SBC _a , pH _a , pCO _2a , BE _a , pO _2a and SO _2a ) can be compared.

The basic assumption involved in this method is that little or no anaerobic metabolism occurs throughout the tissue from which the venous blood sample was taken. If anaerobic metabolism is occurring, this is thought to result in two effects: the base excesses in arterial and venous blood are different, and the strong acid (H ⁺ ) produced by this process has the following reversible effects: In reaction, it will combine with bicarbonate (HCO3 ⁻ ) in the blood to form CO ₂ .
H ⁺ +HCO3 ⁻ ←→CO ₂ +H ₂ O
An increase in _CO2 production due to this response would mean an increase in apparent _VCO2 without an accompanying increase in _VO2 , which can be scaled from venous to arterial values using a constant RQ. means that the conversion to will not be exact. The degree of anaerobic metabolism depends on the circulatory and metabolic state of the patient.

Anaerobic metabolism is unlikely to occur in normally well-perfused peripheral extremities. The quality of limb perfusion can be assessed clinically by the presence of clearly identifiable arterial pulsations determined by palpation, normal capillary response, and normal color and temperature of the limb. Central venous blood or mixed venous blood is a mixture of blood obtained from multiple sites and thus may include blood obtained from areas of the body with anaerobic metabolism. Therefore, the choice of sample site is important.

WO2004/010861 (OBI Medical Aps, to Denmark), which is incorporated herein by reference in its entirety, and Computer methods and programs in biomedicine 81, which is also incorporated herein by reference in its entirety. (2006), pp. 18-25, the related scientific paper by Rees et al., "A method for calculation of arterial acid-base and blood gas status from measurements in the peripheral venous blood."

Figures 2-4 show graphs of oxygen dissociation curves (ODC) in three situations.
When using VTAC to arterialize blood gas values, the method may require input of SO2 _AE . Since oxygen cannot be added to the blood during its passage through tissues, the venous or capillary SO2 in a pair of samples cannot, by definition, be higher than the corresponding arterial SO2. Figures 2-4 show three (3) VBG samples and one (1) ABG recorded in Figures 2, 3, and 4, respectively (but not displayed in all three graphs). ) are combined pairs of ODC curves.

FIG. 2 shows an example where there is a large difference between the oxygen saturation of venous or capillary blood and arterial blood.
FIG. 3 shows examples of very little or no difference between the oxygen saturation of venous or capillary blood and arterial blood.

FIG. 4 shows an example where arterial blood is less saturated than venous/capillary blood (which is not physically plausible and is the result of measurement error or tolerance).
However, in real-world settings, due to preanalytical and analytical errors in blood gas analysis and/or, for example, using pulse oximetry, where the accuracy of the measurements is typically within ±4% (2xSD), When estimating SO2 _AE , a situation such as in FIG. 4 would arise, SO2 _VM would be higher than SO2 _AE . The same situation will arise even more frequently when using the VTAC method to arterialize an incompletely mechanically arterialized capillary blood sample.

In such cases where SO2 _AE is below the oxygen saturation SO2 _VM obtained from blood gas measurements, VTAC using known mechanisms cannot arterialize the blood gas values, thus the clinician must No answer will be given and the measurement will need to be repeated using an alternative method such as normal arterial or capillary blood gas measurement.

The method described in the present invention solves this problem and ensures that clinicians get answers in situations where the data yields clinically relevant results.
The magnitude of this problem becomes apparent when data from clinical trials and customer data from customers using the v-TAC™ method for arterialization of venous or capillary blood are examined.

Based on the data from Table 1 above, up to 10% of patients on pulmonary therapy and capillary blood gas in that the clinician would receive an error message instead of an arterial value. It is estimated that between 20-50% of patients will be affected if .

Advantages of using the present invention VTAC solutions, such as the specific v-TAC™ software, using this method obtain arterialized blood gas and acid-base values for a higher percentage of clinical samples. and almost all situations where venous or capillary blood is already close to arterial blood (depending on the setting) will be able to be resolved, and the answer will certainly be obtained. If the prescription is (for example only, using a cut-off value of 4% as the maximum acceptable difference between SO2 _VM and SO2 _AE , this SO2 _AE is estimated using pulse oximetry): Yields in the patient groups referred to in the section above will increase, as shown below:
if SO2 _VM ≥ SO2 _AE and
1) If SO2 _VM - SpO2 > 4% -> no result 2) If SO2 _VM - SpO2 ≤ 4% -> Use SO2 _VM as SO2 _AE for arterialization

Analysis of the various results presented in Table 2 above indicates that the mathematical arterialization response rate will be significantly enhanced by the method using the settings described. Of the 395 patients, arterialization was not successful in 29 patients without the method, but in only 2 patients with the method according to the present invention. Note that Table 2 shows results from 5 different clinical trials with various patient groups.

Much lower SO2 _AE than SO2 _VM is less likely due to tolerance, but more likely due to pre-analytical or analytical error, in which case these would be discarded. (See example (3) of lung treatment where two samples were untreated because the measured SpO2 was below 4% of the SO2 _VM ).

FIG. 5 is a schematic system chart representing the working overview/details of the method according to the invention.
The present invention, according to one embodiment, changes the SpO2 acceptance criteria from "SpO2>SO2V" to "SpO2>SO2V−K" (K is set at 4(4)%, a variable constant default value) can be run.

4 (4%) was chosen in this embodiment because it is thought to solve the above problem, and 4% is 2xSD commonly applied in pulse oximetry, thus compensating for differences in SpO2 measurements. because it is useful for

According to the above criteria, SpO2 obtained from VBG or CBG (or ABG if the sample is arterial blood) measurements will be used by v-TACT as the SpO2 level in situations below SO2.

In most cases this translates VBG/CBG/ABG measurements directly into the values reported by the v-TAC, but by obtaining this value via the v-TAC software, the DPG tolerance, etc. plausibility check was performed, which would mean that the pO2 level would be cut at 10 kPa.

All measurements that fall into the category SpO2 slightly below SO2V are:
Notification: SpO2 is x% below SO2V; use SO2V as SpO2 for conversion where x = SpO2 - SO2V
will be reported with a notification such as

All measurements where SpO2 is more than 4% below SO2V will trigger an error message such as:
Error: SpO2 is x% less than SO2V;
Risks The potential risks posed by this new acceptance standard have been intensively reviewed over a period of time, but no significant risks have been identified as a result of changes due to:
- SpO2 tolerance remains at 75-100% (constant C in Figure 5).
- If the SpO2 is slightly lower than estimated by the pulse oximeter or was incorrectly entered by the operator, then this SO2 is the value used for conversion.
- If the SpO2 is significantly lower than estimated by pulse oximetry or is incorrectly entered by the operator, the v-TAC will report an error message.

In summary, the present invention provides measurements and/or estimates of arterial oxygenation, e.g. SO2 _AM , _SO2 , based on measurements of blood acid-base status, _{e.g. AE} , for methods for providing SpO2. Transformation of venous blood values is performed by applying a mathematical model to derive the acid-base and oxygenation status of the blood to an estimated or predicted value for arterial blood, eg _ABGP . Further, if the measured and/or estimated arterial oxygenation value is less than the corresponding venous oxygenation value, then the estimated arterial oxygenation value is less than the corresponding venous oxygenation value. It is done with an alternate value that is a function. This advantage is made possible by obtaining arterialized blood gas and acid-base values for a higher proportion of clinical samples than was previously impossible to convert venous values to arterial values. It is the point that it will be.

The invention can be implemented in hardware, software, firmware or any combination thereof. The invention, or some of its features, can also be implemented as software running on one or more data processors and/or digital signal processors, i.e., processing data on one or more computers. be.

The individual elements in embodiments of the invention may be physically, functionally and logically implemented in any suitable way, such as as part of a single unit, multiple units or separate functional units. obtain. The invention may be implemented in a single unit, or may be physically and functionally distributed between different units and processors.

Although the present invention has been described in connection with specific embodiments, it should not be construed as being in any way limited to the examples presented. The scope of the invention should be interpreted in light of the attached set of claims. In the context of a claim, the terms "comprising" or "comprising" do not exclude other possible elements or steps. Similarly, references to designations such as "a" or "an" should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements shown in the figures should also not be construed as limiting the scope of the invention. For this reason, in the claims below, several reference signs, for example:
- SO2 _AM , SO2 _AE and/or SpO2 as measurements and/or estimates of arterial oxygenation
- VBG _M , VBG _E as measurements and/or estimates of blood acid-base status in venous blood samples, and/or - ABG _P as estimates of arterial blood.
are set forth in parentheses, and those skilled in the art will appreciate that certain abbreviations for these measured and/or estimated values have some specific value within the context and principles of the present invention, some of which are also shown in the figures), but other specific values may be applied alternatively or additionally and used for the technical goals and objectives achieved by the present invention. You will easily understand what can be done.

Furthermore, although individual features recited in different claims may be advantageously combined, it is not advantageous to refer to these features in different claims as the combination of features is not possible. does not exclude that

Claims (18)

A computer-implemented method for converting a venous blood value to an arterial blood value, comprising:
a) providing a measure of arterial oxygenation, SO2 _AM or SpO2, and/or an estimate, SO2 _AE ;
b) measuring the blood acid-base status value VBGM and/or estimating the value VBG E _{in a} blood sample obtained from venous blood;
c) transforming the venous blood values by applying a mathematical model to derive the acid-base and oxygenation status of the blood to an estimate of the arterial blood ( _ABGP ), wherein
d1) if the measured and/or estimated arterial oxygenation is below the corresponding venous oxygenation value,
e) next, estimating said arterial oxygenation value using a substitute value that is a function of the corresponding venous oxygenation value. If condition d1) is met, then an additional condition,
d2) As an additional requirement for initiating e), further, the numerical difference between said measured and/or estimated value of arterial oxygenation and said corresponding value of venous oxygenation is equal to a predetermined 2. The method of claim 1, including below a threshold (K). In condition d2), said predetermined threshold (K) is determined by a) the measurement uncertainty of the measuring device used to provide the value of arterial oxygenation and/or b) in a venous blood sample. 3. The method of claim 2, wherein the method is dependent on the measurement uncertainty of the measuring device used to provide the blood acid-base status value. in the step of e) estimating said arterial oxygenation values using alternative values that are functions of corresponding venous oxygenation values, said functions comprising models of arterial blood gas and acid-base conditions; , adjusted to predict arterial oxygenation values. In the step of e) estimating the arterial oxygenation value using a substitute value that is a function of the corresponding venous oxygenation value, the substitute value is equal to the venous oxygenation value. Item 5. The method according to any one of Items 1 to 4. In the step of e) of estimating said arterial oxygenation value using a surrogate value that is a function of the corresponding venous oxygenation value, said surrogate value is a measure of venous blood gas and acid-base status and /or adapted to compensate for one or more pre-analytical and/or analytical errors in the estimation and/or measured arterial oxygenation and/or estimated arterial oxygenation; Item 5. The method according to any one of Items 1 to 4. In the step of e) of estimating said arterial oxygenation values using surrogate values that are functions of corresponding venous oxygenation values, said surrogate values are derived from arterial blood gas and acid-base status (ABG) and venous blood gases and acid-base status (VBG), adapted to complement the expected minimal oxygen metabolism Method. in the step of e) estimating said arterial oxygenation values using alternative values that are functions of corresponding venous oxygenation values, said functions comprising models of arterial blood gas and acid-base conditions; , adjusted to predict arterial oxygenation values using measured venous blood gases and acid-base status (VBG _M ) and/or estimated venous blood gases and acid-base status, claim Item 8. The method of any one of Items 1 to 7. The measured venous blood gases and acid-base status (VBG _M ) are further corrected to compensate for one or more analytical errors in the measurement of venous blood gases and acid-base status (VBG _M ). 9. The method of claim 8. wherein said measured venous blood gases and acid-base status (VBG _M ) provide corresponding differences between arterial blood gases and acid-base status (ABG) and venous blood gases and acid-base status (VBG); 10. The method of claim 8 or 9, further corrected to complement the predicted minimum oxygen metabolism. The process of c) converting the venous blood values by applying a mathematical model to derive the acid-base and oxygenation status of the blood to an estimate of the arterial blood ( _ABGP ) is the venous blood measurement. 11. The method of any one of claims 1 to 10, wherein ( _VBGM ) is modified in that oxygen is removed and/or carbon dioxide is added for modeling purposes. Method. 12. The method of claim 11, wherein oxygen is removed and/or carbon dioxide is added for modeling purposes limited to a range of physiologically possible values. 13. The method of claim 12, wherein the arterial blood estimate is calculated within the range of physiologically possible values. 3. The method of claim 2, wherein in condition d2), the predetermined threshold (K) is dependent on a physiologically based safety margin. The mathematical model predicts that the true value of respiratory quotient (RQ) in tissue is 0.7 for aerobic metabolism of lipids and 1.0 for aerobic metabolism of carbohydrates, and between 0.7 and 1.0. 2. The method of claim 1, applying that only . The mathematical model adds _O2 and _CO2 from venous blood at a rate determined by a constant respiratory quotient (RQ) set within the physiologically possible range of 0.7-1.0. and performing the simulation until the simulated oxygen saturation equals or substantially equals the oxygen saturation estimated or measured in arterial blood, 16. The method of claim 1 or 15. A data processing system for converting venous blood values to arterial blood values, comprising:
- means for providing a measure of arterial oxygenation, SO2 _AM or SpO2, and/or an estimate, SO2 _AE ;
- means for measuring the blood acid-base value VBGM and/or estimating the value _{VBGE E in} a blood sample obtained from venous blood; transforming the venous blood values by applying a mathematical model to derive an estimate of the arterial blood ( _ABGP );
wherein if the measured and/or estimated arterial oxygenation value is below the corresponding venous oxygenation value, then with a substitute value that is a function of the corresponding venous oxygenation value, A data processing system comprising means for estimating a value of said arterial oxygenation. A computer program product that enables a computer system to perform the operations of the system of claim 17 when downloaded to or uploaded to that computer system.

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